A digital image is a collection of pixels, typically arranged in an array, which defines an optically formed reproduction of one or more objects, backgrounds or other features of a scene. In a digital image, each of the pixels represents or identifies a color or other light condition associated with a portion of such objects, backgrounds or features. For example, a black-and-white digital image includes a single bit for representing a light condition of the pixel in a binary fashion (e.g., either black or white), while a grayscale digital image may represent a light condition in multiple bits (e.g., two to eight bits for defining tones of gray in terms of percentages or shares of black-and-white). A color digital image may include groups of bits corresponding to each of a plurality of base colors (e.g., red, green or blue), and the groups of bits may collectively represent a color associated with the pixel. One common digital image is a twenty-four bit (24-bit) color digital image, in which each of the pixels includes three channels of eight bits each, including a first channel of eight bits for describing an extent of red within a pixel, a second channel of eight bits for describing an extent of green within the pixel, and a third channel of eight bits for describing an extent of blue within the pixel.
Steganography is the art and science of sending and receiving communications in a manner that prevents their presence from being detected. The word “steganography,” which literally means “covered writing” in Greek, is commonly used to describe communications techniques in which invisible or subliminal messages are hidden within digital images. A steganographic process starts by selecting content that is to be concealed, and by identifying portions of a base image, e.g., an image having one or more bits that may be modified to encode the content without damaging the integrity or size of the base image. Such bits, which are sometimes referred to as “least significant bits,” “less significant bits,” or “redundant bits,” may be co-opted and replaced with data corresponding to the content to be concealed. By its very nature, steganographic conversion and storage of data within a base image necessarily reduces the clarity and resolution of the base image, to at least a very limited extent. Where the bits of the base image are properly selected, however, information or data may be concealed within a base image in a manner that is indiscernible to the human eye, and which neither increases nor decreases a total number of bits occupied by the modified base image, thereby ensuring that a size of a file including the modified base image is no larger than a size of the base image itself.